A snowstorm is dropping huge amounts of flakes in the northern and eastern parts of the United States, snarling air traffic.

Temperatures are also drastically lower for this time of year. On Tuesday morning, the national average was 19.4 degrees F., according to forecasters.

All 50 states have seen freezing temperatures, the National Weather Service reports. Tuesday, in fact, brought the coldest November morning since 1976, writes WeatherBell meteorologist Ryan Maue. Temperatures in recent days have fallen 10 degrees C (about 18 degrees F.) below normal, Dr. Maue says, adding that this is "more anomalous" than this past January, when the polar vortex brought frigid temperatures.

But the amount of snowfall varies from location to location. "There are places that are getting 40 inches of snow, and five miles away they have a couple inches," Mr. Kines said.

While the Lower 48 states have borne the brunt of a jet stream pattern that's funneled Arctic air southward, the jet stream has channeled relatively milder air toward Alaska, The Washington Post says. It notes that the average temperature of the Lower 48 Tuesday morning was roughly equivalent to Barrow, Alaska, the state's northernmost town.